U.S. patent number 5,127,232 [Application Number 07/612,643] was granted by the patent office on 1992-07-07 for method and apparatus for recovering and purifying refrigerant.
This patent grant is currently assigned to Carrier Corporation. Invention is credited to Lowell E. Paige, Chester D. Ripka.
United States Patent |
5,127,232 |
Paige , et al. |
July 7, 1992 |
Method and apparatus for recovering and purifying refrigerant
Abstract
A method and apparatus for recovering and purifying refrigerant
contained in a refrigeration system has a first mode of operation
wherein refrigerant is withdrawn from the system being serviced,
compressed, condensed and delivered in liquid form to a refrigerant
storage means. The pressure ratio across the recovery compressor is
monitored, and, when the pressure ratio exceeds a value above which
the compressor may be adversely affected withdrawal of the
refrigerant from the refrigeration system is terminated. The system
is then operated in a closed, cooling mode wherein refrigerant
recovered from the system and stored in the storage means is
withdrawn therefrom by the compressor, compressed condensed, and
expanded and returned to the storage means to thereby lower the
temperature and pressure of the storage means and the refrigerant
contained therein. Means for purifying the withdrawn refrigerant
are located upstream from the compressor suction port so that
refrigerant purification takes place during all modes of operation.
When the temperature in the refrigerant storage cylinder falls to a
predetermined level the system is returned to the recovery mode.
During the second recovery cycle, because of the substantially
lower temperature in the recovery system, the refrigerant storage
cylinder effectively serves as a condenser.
Inventors: |
Paige; Lowell E. (Penneville,
NY), Ripka; Chester D. (E. Syracuse, NY) |
Assignee: |
Carrier Corporation (Syracuse,
NY)
|
Family
ID: |
24454034 |
Appl.
No.: |
07/612,643 |
Filed: |
November 13, 1990 |
Current U.S.
Class: |
62/77; 62/149;
62/292; 62/475; 62/85 |
Current CPC
Class: |
F25B
45/00 (20130101); F25B 2345/002 (20130101) |
Current International
Class: |
F25B
45/00 (20060101); F25B 045/00 () |
Field of
Search: |
;62/77,85,149,292,475,529,83,503,174 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Makay; Albert J.
Assistant Examiner: Sollecito; John
Claims
What is claimed is:
1. Apparatus for recovering compressible refrigerant from a
refrigeration system comprising;
compressor means for compressing gaseous refrigerant delivered
thereto, said compressor means having a suction port and a
discharge port;
first conduit means for connecting the refrigeration system to said
suction port of said compressor means;
condenser means for passing refrigerant therethrough, said
condenser means having an inlet and an outlet;
second conduit means for connecting said discharge port of said
compressor means with said inlet of said condenser means;
means for storing refrigerant;
third conduit means for connecting said outlet of said condenser
means with said means for storing refrigerant;
fourth conduit means for connecting said means for storing
refrigerant with said first conduit means;
first valve means operable between open and shut conditions and
disposed in said first conduit means upstream from the connection
of said fourth conduit means with said first conduit means;
second valve means operable between an open condition and an
refrigerant expanding condition and disposed in said third conduit
means;
third valve means operable between open and shut conditions and
disposed in said fourth conduit means;
means for sensing a system control parameter related to protection
of said compressor, and, for providing a signal having a value
indicative of the sensed system control parameter; and
processor means for receiving said signal provided by said sensing
means, and, for operating said first valve means to an open
condition, said second valve means to an open condition, and, said
third valve means to a closed condition in response to said signal
having a value within a predetermined range at which said
compressor is not adversely effected; and, for operating said first
valve means to a shut condition, said second valve means to a
refrigerant expanding condition, and, said third valve means to an
open condition in response to said signal having a value within a
predetermined range at which said compressor is adversely
effected.
2. The apparatus of claim 1 wherein said means for sensing a system
control parameter comprises;
a first pressure transducer means for sensing the pressure of
refrigerant entering said compressor and for providing a first
pressure signal indicative of this pressure; and
a second pressure transducer means for sensing the pressure of
refrigerant leaving said compressor and for providing a second
pressure signal indicative of this pressure;
means for processing said first pressure signal and said second
pressure signal to provide said signal having a value indicative of
the sensed control parameter.
3. The apparatus of claim 2 wherein said means for processing said
first pressure signal and said second pressure signal determines
the pressure ratio across said compressor, said sensed system
control parameter being compressor pressure ratio.
4. The apparatus of claim 2 wherein said means for processing said
first pressure signal and said second pressure signal determines
the pressure differential across said compressor, said sensed
system control parameter being compressor pressure
differential.
5. The apparatus of claim 1 further including means for purifying
refrigerant, said means for purifying being disposed in said first
conduit means.
6. The apparatus of claim 5 wherein said means for purifying
refrigerant comprises;
means for removing oil from refrigerant passing therethrough;
and
means for removing acid, water and particulate contaminants from
the refrigerant passing therethrough.
7. The apparatus of claim 5 further including liquid refrigerant
accumulator means disposed in said conduit means.
8. The apparatus of claim 1 wherein said second valve means
comprises;
a flow control valve operable between open and shut condition;
and
a refrigerant expansion means;
said flow control valve and said refrigerant expansion means being
disposed in parallel fluid flow relationship in said third
conduit.
9. The apparatus of claim 1 wherein said means for sensing
comprises a temperature transducer positioned to measure the
temperature of refrigerant being discharged from said compressor
means whereby said system control parameter is the compressor
discharge temperature.
10. The apparatus of claim 1 wherein said means for sensing
comprises a pressure transducer positioned to measure the
refrigerant pressure at said suction port of said compressor means,
whereby said system control parameter is compressor suction
pressure.
11. Apparatus for recovering compressible refrigerant from a
refrigeration system comprising;
compressor means for compressing gaseous refrigerant delivered
thereto, said compressor means having a suction port and a
discharge port;
first conduit means for connecting the refrigeration system to said
suction port of said compressor means;
condenser means for withdrawing heat from and at least partially
condensing refrigerant passing therethrough, said condenser means
having an inlet and an outlet;
second conduit means for connecting said discharge port of said
compressor means with said inlet of said condenser means;
means for storing refrigerant;
third conduit means for connecting said outlet of said condenser
means with said means for storing refrigerant;
fourth conduit means for connecting said means for storing
refrigerant with said first conduit means;
first valve means operable between open and shut conditions and
disposed in said first conduit means upstream from the connection
of said fourth conduit means with said first conduit means;
second valve means operable between an open condition and a
refrigerant expanding condition and disposed in said third conduit
means;
third valve means operable between open and shut conditions and
disposed in said fourth conduit means;
first pressure transducer means for sensing the pressure of
refrigerant prior to entering said compressor and for providing a
first signal indicative of this sensed pressure;
second pressure transducer means for sensing the pressure of
refrigerant leaving said compressor and for providing a second
signal indicative of this sensed pressure;
processor means for receiving the first and second signals provided
by said first and second sensor means, for processing the received
signals to determine a pressure ratio across the compressor, and,
for operating said first valve means to an open position, said
second valve means to an open condition and said third valve means
to a shut condition in response to said determined pressure ratio
being lower than a predetermined value; and for operating said
first valve means to a shut condition, said second valve means to a
refrigerant expanding condition, and, said third valve means to an
open condition in response to said determined pressure ratio
exceeding a predetermined value.
12. A method for recovering compressible refrigerant from a
refrigeration system, and, delivering the recovered refrigerant to
a refrigeration storage means comprising sequentially the steps
of;
a. withdrawing refrigerant from a refrigeration system;
b. compressing the withdrawn refrigerant in a compressor to form a
high pressure gaseous refrigerant;
c. condensing the high pressure gaseous refrigerant to form liquid
refrigerant;
d. delivering the liquid refrigerant to the storage means;
e. determining the pressure ratio across the compressor;
f. monitoring the determined pressure ratio;
g. stopping the withdrawal of refrigerant from the refrigeration
system when the monitored pressure ratio exceeds a predetermined
value;
h. withdrawing refrigerant from the storage means;
i. compressing the refrigerant withdrawn from the storage means in
the same compressor used to compress refrigerant withdrawn from the
refrigeration system;
j. condensing the compressed refrigerant withdrawn from the storage
means;
k. expanding the condensed refrigerant withdrawn from the storage
means;
l. delivering the expanded refrigerant withdrawn from the storage
means back to the storage means to thereby cool the storage
means;
m. sequentially repeating steps h, i, j, k and 1;
n. while performing step m, monitoring the temperature of the
storage means;
o. stopping the withdrawal of refrigerant from the storage means
when the temperature of the storage means falls below a
predetermined value;
p. resuming withdrawal of refrigerant from the refrigeration system
when the temperature of the storage means falls below said
predetermined value;
q. monitoring the suction pressure of the compressor; and
r. terminating the recovery operation when the suction pressure of
the compressor falls below a predetermined value.
13. A method for recovering compressible refrigerant from a
refrigeration system and delivering the recovered refrigerant to a
refrigeration storage means comprising, sequentially, the steps
of;
a. withdrawing refrigerant from a refrigeration system;
b. compressing the withdrawn refrigerant in a compressor to form a
high pressure gaseous refrigerant;
c. condensing the high pressure gaseous refrigerant to form liquid
refrigerant;
d. delivering the liquid refrigerant to the storage means;
e. monitoring the temperature of the refrigerant being discharged
from the compressor;
f. stopping the withdrawal of refrigerant from the refrigeration
system when said monitored temperature exceeds a predetermined
value;
g. withdrawing refrigerant from the storage means;
h. compressing the refrigerant withdrawn from the storage means in
the same compressor used to compress refrigerant withdrawn from the
refrigeration system;
i. condensing the compressed refrigerant withdrawn from the storage
means;
j. expanding the condensed refrigerant withdrawn from the storage
means;
k. delivering the expanded refrigerant withdrawn from the storage
means back to the storage means to thereby cool the storage
means;
l. repeating steps g,h,i,j and k;
m. while performing step 1, monitoring the temperature of the
storage means;
n. stopping the withdrawal of refrigerant from the storage means
when the temperature of said storage means falls below a
predetermined value;
o. resuming withdrawal of refrigerant from the refrigeration system
when the temperature of the storage means falls below said
predetermined value;
p. monitoring the suction pressure of the compressor; and
q. terminating the recovery operation when the suction pressure of
the compressor falls below a predetermined value.
14. A method for recovering compressible refrigerant from a
refrigeration system and delivering the recovered refrigerant to a
refrigeration storage means comprising, sequentially, the steps
of;
a. withdrawing refrigerant from a refrigeration system;
b. compressing the withdrawn refrigerant in a compressor to form a
high pressure gaseous refrigerant;
c. condensing the high pressure gaseous refrigerant to form liquid
refrigerant;
d. delivering the liquid refrigerant to the storage means;
e. monitoring the suction pressure of the refrigerant
compressor;
f. stopping the withdrawal of refrigerant from the refrigeration
system when said monitored suction pressure falls below a
predetermined value;
g. withdrawing refrigerant from the storage means;
h. compressing the refrigerant withdrawn from the storage means in
the same compressor used to compress refrigerant withdrawn from the
refrigeration system;
i. condensing the compressed refrigerant withdrawn from the storage
means;
j expanding the condensed refrigerant withdrawn from the storage
means;
k. delivering the expanded refrigerant withdrawn from the storage
means back to the storage means to thereby cool the storage
means;
l. repeating steps g,h,i,j and k;
m. while performing step 1, monitoring the temperature of the
storage means;
n. stopping the withdrawal of refrigerant from the storage means
when the temperature of said storage means falls below a
predetermined value;
o. resuming withdrawal of refrigerant from the refrigeration system
when the temperature of the storage means falls below said
predetermined value; and
p. terminating the recovery operation when the suction pressure of
the compressor falls below a second predetermined minimum
value.
15. The method of claims 12, 13, or 14, further including the step
of purifying the withdrawn refrigerant, performed between steps a
and b.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the recovery of, and purification of,
compressible refrigerant contained in a refrigeration system. More
specifically it relates to a method and apparatus for recovering an
extremely high percentage of the refrigerant contained in a given
system.
2. Description of The Prior Art
A wide variety of mechanical refrigeration systems are currently in
use in a wide variety of applications. These applications include
domestic refrigeration, commercial refrigeration, air conditioning,
dehumidifying, food freezing, cooling and manufacturing processes,
and numerous other applications. The vast majority of mechanical
refrigeration systems operate according to similar, well known
principals, employing a closed-loop fluid circuit through which a
refrigerant flows. A number of saturated fluorocarbon compounds and
azeotropes are commonly used as refrigerants in refrigeration
systems. Representative of these refrigerants are R-12, R-22, R-500
and R-502.
Those familiar with mechanical refrigeration systems will recognize
that such systems periodically require service. Such service may
include removal, of, and replacement or repair of, a component of
the system. Further during normal system operation the refrigerant
can become contaminated by foreign matter within the refrigeration
circuit, or by excess moisture in the system. The presence of
excess moisture can cause ice formation in the expansion valves and
capillary tubes, corrosion of metal, copper plating and chemical
damage to insulation in hermetic compressors. Acid can be present
due to motor burn out which causes overheating of the refrigerant.
Such burn outs can be temporary or localized in nature as in the
case of a friction producing chip which produces a local hot spot
which overheats the refrigerant. The main acid of concern is HCL
but other acids and contaminants can be produced as the
decomposition products of oil, insulation, varnish, gaskets and
adhesives. Such contamination may lead to component failure or it
may be desirable to change the refrigerant to improve the operating
efficiency of the system.
When servicing a refrigeration system it has been the practice for
the refrigerant to be vented into the atmosphere, before the
apparatus is serviced and repaired. The circuit is then evacuated
by a vacuum pump, which vents additional refrigerant to the
atmosphere, and recharged with new refrigerant. This procedure has
now become unacceptable for environmental reasons, specifically, it
is believed that the release of such fluorocarbons depletes the
concentration of ozone in the atmosphere. This depletion of the
ozone layer is believed to adversely impact the environment and
human health. Further, the cost of refrigerant is now becoming an
important factor with respect to service cost, and such a waste of
refrigerant, which could be recovered, purified and reused, is no
longer acceptable.
To avoid release of fluorocarbons into the atmosphere, devices have
been provided that are designed to recover the refrigerant from
refrigeration systems. The devices often include means for
processing the refrigerants so recovered so that the refrigerant
may be reused. Representative examples of such devices are shown in
the following U.S. Pat. Nos.: 4,441,330 "Refrigerant Recovery And
Recharging System" to Lower et al; 4,476,688 "Refrigerant Recovery
And Purification System" to Goddard; 4,766,733 "Refrigerant
Reclamation And Charging Unit" to Scuderi; 4,809,520 "Refrigerant
Recovery And Purification System" to Manz et al; 4,862,699 "Method
And Apparatus For Recovering, Purifying and Separating Refrigerant
From Its Lubricant" to Lounis; 4,903,499 "Refrigerant Recovery
System" to Merritt; and 4,942,741 "Refrigerant Recovery Device" to
Hancock et al.
When most such systems are operating, a recovery compressor is used
to withdraw the refrigerant from the unit being serviced. As the
pressure in the unit being serviced is drawn down, the pressure
differential across the recovery compressor increases because the
pressure on the suction side of the compressor becomes increasingly
lower while the pressure on the discharge side of the compressor
stays constant. High compressor pressure differentials can be
destructive to compressor internal components because of the
unacceptably high internal compressor temperatures which accompany
them and the increased stresses on compressor bearing surfaces.
Limitations on the pressure differentials or pressure ratio across
the recovery compressors are thus necessary, such limitations, in
turn can limit the percentage of the total charge of refrigerant
contained within the unit being serviced that may be successfully
recovered.
SUMMARY OF THE INVENTION
It is an object of the present invention to withdraw an extremely
high percentage of the refrigerant from a refrigeration system
being serviced.
It is another object of the invention to recover a high percentage
of the refrigerant charge from a system being serviced without
subjecting the compressor of the recovery system to adverse
operating conditions.
A further object of the invention is to operate a refrigerant
recovery system in alternating modes of operation, a first mode
recovers refrigerant, and, a second mode lowers the temperature and
pressure of the recovered refrigerant in the recovery system to
thereby facilitate recovery of refrigerant in a subsequent recovery
cycle.
Yet another object of the invention is to operate a refrigerant
recovery system in several modes of operation, and, carrying out
refrigerant purification during all modes.
These and other objects of the invention are carried out by
providing an apparatus and method for recovering compressible
refrigerant from a refrigeration system and delivering the
recovered refrigerant to a refrigeration storage means. The
recovery method includes the steps of withdrawing refrigerant from
a refrigeration system being serviced and compressing the withdrawn
refrigerant in a compressor to form a high pressure gaseous
refrigerant. The high pressure gaseous refrigerant is delivered to
a condenser where it is condensed to form liquid refrigerant. The
liquid refrigerant from the condenser is delivered to the
refrigerant storage means. Means are provided for determining the
pressure ratio across the recovery system compressor and monitoring
the determined pressure ratio. When the monitored pressure ratio
exceeds a predetermined value above which the compressor may be
adversely affected the system is caused to stop the withdrawal of
refrigerant from the refrigeration system being serviced.
At that point, the system begins to withdraw stored refrigerant
from the storage means. The refrigerant withdrawn from the storage
means is then compressed in the same compressor which was used to
compress refrigerant withdrawn from the refrigeration system. This
refrigerant is then condensed to form liquid refrigerant which is
then passed through a suitable expansion device and delivered back
to the storage means to thereby cool the storage means and the
refrigerant contained therein. This cooling cycle is performed for
a period of time until the temperature of the storage means falls
to a predetermined value. At that point the system resumes
withdrawal of refrigerant from the refrigeration system being
serviced. When the suction pressure of the recovery system
compressor falls below a predetermined value the recovery operation
is terminated.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features that are considered characteristic of the
invention are set forth with particularity in the appended claims.
The invention itself, however, both as to its organization and its
method of operation, together with additional objects and
advantages thereof, will be best understood from the following
description of the preferred embodiment when read in connection
with the accompanying drawings wherein;
FIG. 1 is a diagrammatical representation of a refrigeration
recovery and purifying system embodying the principles of the
present invention;
FIG. 2 is a flow chart of an exemplary program for controlling the
elements of the present invention in a recovery cycle;
FIG. 3 is a flow chart of an exemplary program for controlling the
element of the present invention in a recycle mode of operation;
and
FIG. 4 is a chart showing the operation of the various components
of a system according to the present invention during different
modes of system operation.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An apparatus for recovering and purifying the refrigerant contained
in a refrigeration system is generally shown at reference numeral
10 in FIG. 1. The refrigeration system to be evacuated is generally
indicated at 12 and may be virtually any mechanical refrigeration
system.
As shown the interface or tap between the recovery and purification
system 10 and the system being serviced 12 is a standard gauge and
service manifold 14. The manifold 14 is connected to the
refrigeration system to be serviced in a standard manner with one
line 16 connected to the low pressure side of the system 12 and
another line 18 connected to the high pressure side of the system.
A high pressure refrigerant line 20 is interconnected between the
service connection 22 of the service manifold and an appropriate
coupling (not shown) for coupling the line 20 to the recovery
system 10.
The recovery system 10 includes two sections, as shown in FIG. 1
the components and controls of the recovery system are contained
within a self contained compact housing (not shown) schematically
represented by the dotted line 24. A refrigerant storage section of
the system is contained within the confines of the dotted lines 26.
The details of each of these sections and their interconnection and
interaction with one another will now be described in detail.
Refrigerant flowing through the interconnecting line 20 flows
through an electrically acuatable solenoid valve SV3 which will
selectively allow refrigerant to pass therethrough when actuated to
its open position or will prevent the flow of refrigerant
therethrough when electrically actuated to its closed position.
Additional electrically actuatable solenoid valves contained in the
system operate in the same conventional manner. From SV3
refrigerant passes through a conduit 28 through a check valve 98 to
a second electrically acuatable solenoid valve SV2. From SV2 an
appropriate conduit 30 conducts the refrigerant to the inlet of a
combination accumulator/oil trap 32 having a drain valve 34.
Refrigerant gas is then drawn from the oil trap through conduit 36
to an acid purification filter-dryer 38 where impurities such as
acid, moisture, foreign particles and the like are removed before
the gases are passed via conduit 40 to the suction port 42 of the
compressor 44. A suction line accumulator 46 is disposed in the
conduit 42 to assure that no liquid refrigerant passes to the
suction port 42 of the compressor. The compressor 44 is preferably
of the rotary type, which are readily commercially available from a
number of compressor manufacturers but may be of any type such as
reciprocating, scroll or screw.
From the compressor discharge port 48 gaseous refrigerant is
directed through conduit 50 to a conventional float operated oil
separator 52 where oil from the recovery system compressor 44 is
separated from the gaseous refrigerant and directed via float
controlled return line 54 to the conduit 40 communicating with the
suction port of the compressor. From the outlet of the oil
separator 52 gaseous refrigerant passes via conduit 56 to the inlet
of a heat exchanger/condenser coil 60. An electrically actuated
condenser fan 62 is associated with the coil 60 to direct the flow
of ambient air through the coil as will be described in connection
with the operation of the system.
From the outlet 64 of the condenser coil 60 an appropriate conduit
66 conducts refrigerant to a T-connection 68. From the T 68 one
conduit 70 passes to another electrically actuated solenoid valve
SV4 while the other branch 72 of the T passes to a suitable
refrigerant expansion device 74. In the illustrated embodiment the
expansion device 74 is a capillary tube and a strainer 76 is
disposed in the refrigerant line 72 upstream from the capillary
tube to remove any particles which might potentially block the
capillary. It should be appreciated that the expansion device could
comprise any of the other numerous well known refrigerant expansion
devices which are widely commercially available. The conduit 72
containing the expansion device 74 and the conduit 70 containing
the valve SV4 rejoin at a second T connection 78 downstream from
both devices. It will be appreciated that the solenoid valve SV4
and the expansion device 74 are in a parallel fluid flow
relationship. As a result, when the solenoid valve SV4 is open the
flow of refrigerant will be, because of the high resistance of the
expansion device, through the solenoid valve in a substantially
unrestricted manner. On the other hand, when the valve SV4 is
closed, the flow of refrigerant will be through the high resistance
path provided by the expansion device. Combination devices such as
electronically actuated expansion valves are known which would
combine the functions of the valves SV4 and the capillary tube 74,
however, as configured and described above, the desired function is
obtained at a minimum cost.
From the second T-78 a conduit 80 passes to an appropriate coupling
(not shown) for connection of the system as defined by the confines
of the line 24, via a flexible refrigerant line 82 to the liquid
inlet port 84 of a refillable refrigerant storage container 86. The
container 86 is of conventional construction and includes a second
port 88 adapted for vapor outlet. The storage cylinder 86 further
includes a noncondensible purge outlet 90 and is further provided
with a liquid level indicator 92. The liquid level indicator, for
example, may comprise a compact continuous liquid level sensor of
the type available from Imo Delaval Inc., Gems Sensors Division.
Such an indicator is capable of providing an electrical signal
indicative of the level of the refrigerant contained within the
storage cylinder 86.
Refrigerant line 94 interconnects the vapor outlet 88 of the
cylinder 86 with a T connection 96 in the conduit 28 extending
between solenoid valve SV3 and solenoid valve SV2. An additional
electrically actuated solenoid valve SVI is located in the line 94.
A check valve 98 is also positioned in the conduit 28 at a location
downstream of the T-96 which is adapted to allow flow in the
direction from SV3 to SV2 and to prevent flow in the direction from
SV2 to SV3.
With continued reference to FIG. 1 a refrigerant gas contamination
detection circuit 100 is included in the system in a parallel fluid
flow arrangement with the compressor 44. The contamination
detection circuit 100 includes an inlet conduit 102 in fluid
communication with the conduit 56 extending from the oil separator
52 to the condenser inlet 58. The inlet conduit 102 has an
electrically actuated solenoid valve SV6 disposed there along and
from there passes to the inlet of a sampling tube holder 104. The
outlet of the sampling tube holder 104 is interconnected via
conduit 106 with the conduit 40 which communicates with the suction
port 42 of the compressor. An electrically controlled solenoid
valve SV5 is disposed in the conduit 106.
The solenoid valves SV5 and SV6, when closed, isolate the sampling
tube holder 104 from the system and allow easy replacement of the
sampling tube contained therein. The sampling tube holder may be of
the type described in U.S. Pat. No. 4,389,372 Portable Holder
Assembly for Gas Detection Tube. Further, the refrigerant
contaminant testing system is preferably of the type shown and
described in detail in U.S. Pat. No. 4,923,806 entitled Method and
Apparatus For Refrigerant Testing In A Closed System and assigned
to the assignee of the present invention. Each of the above
identified patents is hereby incorporated herein by reference in
its entirety.
Automatic control of all of the components of the refrigerant
recovery system 10 is carried out by an electronic controller 108
which is formed of a micro-processor having a memory storage
capability and which is micro-programmable to control the operation
of all of the solenoid valves SVI through SV6 as well as the
compressor motor and the condenser fan motor. Inputs to the
controller 108 include a number of measured or sensed system
control parameters. In the embodiment disclosed these control
parameters include the temperature of the storage cylinder Tstor
which comprises a temperature transducer capable of accurately
providing a signal indicative of the temperature of the refrigerant
in the storage cylinder 86. Ambient temperature is measured by a
temperature transducer positioned at the inlet to the condenser
coil or condenser fan 62 and is referred to as Tamb. The
temperature of the refrigerant flowing through the compressor
discharge line 50 is sensed by a temperature transducer 110
positioned on the compressor discharge line 50.
Most important in the control scheme of the present invention are
the compressor suction pressure designated as P2 and the compressor
discharge pressure designated as P3. As indicated in FIG. 1 a
pressure transducer labeled P2 is in fluid flow communication with
the suction line 40 to the compressor while a second pressure
transducer P3 is in fluid communication with the high pressure
refrigerant line 56 passing to the condenser. The pressure ratio
across the compressor 44 is defined as the ratio P3/P2. An
additional input to the controller 108 is the signal from the
liquid level indicator 92.
Looking now at FIG. 4 it will be noted that the operating modes of
the system are identified and the condition of the electrically
acutable components of the system are shown in the different modes.
In the Standby mode the system has been turned on and all
electrically actuatable mechanical systems are de-energized and
ready for operation. In the Service mode, the electrically actuated
solenoid valves SVl through SV4 are all open thereby equalizing the
pressures within the system so that it may be serviced without fear
of encountering high pressure refrigerant.
The Recover and Cylinder Cool modes will now be described in detail
in connection with the flow chart of FIG. 2. The Recover mode is
the mode in which the device 10 has been coupled to an air
conditioning system 12 for removal of refrigerant therefrom.
Looking now to FIG. 2 it will be noted that the first step
performed by the controller 108 when the Recover cycle is selected
is to compare the compressor discharge pressure P3 to the
compressor inlet pressure P2. If the pressure differential (P3-P2)
is greater than 30 psi the controller 108 will open valves SV1-SV4
in order to equalize the pressures within the system. When the
difference between P3 and P2 falls to less than 10 psi the system
will then go to the Recover mode of operation. If the initial
comparison of P3 and P2 shows a difference of less than or equal to
30 psi the system will go directly to the Recover mode. The reason
for this comparison is that the compressor may readily start up
when the pressure differential is less than or equal to 30 psi,
whereas, when the pressure differential is greater than 30 psi,
compressor start up is difficult and dictates a reduction in the
pressure difference thereacross.
Upon initiation of the Recover mode the controller 108 will open
valves SV2, SV3 and SV4, valve SV1 will remain closed. Valves SV5
and SV6 as noted in FIG. 4 operate together as a single output from
the micro-processor (controller) and the only time is being carried
out. These valves will not be discussed further in connection with
the other modes of operation of the system. The compressor 44 and
the condenser fan 62 are also actuated upon initiation of the
Recover mode.
Looking now at operation of the system in the Recover mode, and
referring to FIG. 1, with valve SV3 open refrigerant from the
system being serviced 12 is forced by the pressure of the
refrigerant in the system, and by the suction created by operation
of the compressor 44, through conduit 20, through valve SV3, check
valve 98, valve SV2 and conduit 30 to the accumulator/oil trap 32.
Within the accumulator/oil trap the oil contained in the
refrigerant being removed from the system being serviced falls to
the bottom of the trap along with any liquid refrigerant withdrawn
from the system. Gaseous refrigerant is drawn from the
accumulator/oil trap 32 through the filter dryer 38 where moisture,
acid and any particulate matter is removed therefrom, and, from
there passes via conduit 40, through the suction accumulator 46 to
the compressor 44.
The compressor 44 compresses the low pressure gaseous refrigerant
entering the compressor into a high pressure gaseous refrigerant
oil separated from the high pressure gaseous refrigerant in the
separator 52 is the oil from the recovery compressor 44 and this
oil is returned via conduit 54 to the suction line 40 of the
compressor to assure lubrication of the compressor. From the oil
separator 52 the high pressure gaseous refrigerant passes via
conduit 56 to the condenser coil 60 where the hot compressed gas
condenses to a liquid. Liquified refrigerant leaves the condensing
coil 60 via conduit 66 and passes through the T68 through the open
solenoid valve SV4, and passes via the liquid lines 80 and 82, to
the refrigerant storage cylinder 86 through liquid inlet port
84.
While refrigerant recovery is going on the controller 108 is
receiving signals from the pressure transducers P3 and P2,
calculating the pressure ratio P3/P2, and, comparing the calculated
ratio to a predetermined value. Compressor suction pressure P2 is
also being looked at alone and being compared to a predetermined
Recovery Termination Suction Pressure. As shown in FIG. 2, the
predetermined Recovery Termination Suction Pressure is 4 psia, and
if P2 falls below this value the Recover mode is terminated and the
controller 108 initiates the refrigerant quality test cycle,
identified as Totaltest. This cycle will be described below
following a complete description of the other modes of operation.
TOTALTEST is a registered Trademark of Carrier Corporation for
"Testers For Contaminants in A Refrigerant".
The selection of the predetermined recovery termination suction
pressure of 4 psia results from recovery system operation wherein
it has been shown that a compressor suction pressure, P2, of 4 psia
or less results in recovery of 98 to 99% of the refrigerant from
the system being serviced Achieving this pressure during the first
Recover mode cycle is unusual, however, it is achievable. As an
example, P2 may be drawn down to the 4 psia termination value in
low ambient temperature conditions where the condensing coil
temperature (which is ambient air cooled) is low enough to allow P3
to remain low enough for P2 to reach 4 psia before the pressure
ratio limit is reached.
Returning now to compressor pressure ratio, as indicated in FIG. 2,
in the illustrated embodiment, when the pressure ratio exceeds or
is equal to 16 the microprocessor in the controller 108 performs
what is referred to as the Recovery Cycle Test. If the Recovery
Cycle just performed is the first Recovery Cycle performed and the
compressor suction pressure P2 is greater than or equal to 10 psia
the system will shift to what is known as a Cylinder Cool mode of
operation. If the Recovery Cycle just performed is a second or
subsequent recovery cycle and the compressor suction pressure P2 is
less than 10 psia the controller will consider the refrigerant
Recovery as completed and will initiate the refrigerant contaminant
test cycle (Totaltest).
The latter conditions, i.e. second or subsequent recover cycle, and
P2 less than 10 psia, are conditions that are found to exist at
high ambient temperatures. For example, such conditions may exist
when recovering R-22 from an air conditioning system at an ambient
temperature of 105.degree. F. and above. Under such conditions it
has been found that attempts to reduce the compressor suction
pressure P2 to values less than 10 psia are counterproductive in
that a substantial length of operating time would be necessary in
order to obtain a very small additional drop in suction pressure.
Further, it has been found, at these conditions, that shifting to
the Cylinder Cool mode, which will be described below, also would
not substantially increase the amount of refrigerant that would
ultimately be withdrawn from the system and accordingly termination
of the Recover mode and initiation of the refrigerant contaminant
test cycle is indicated.
Assuming that the Recovery Cycle Test has indicated that either: it
is the first recovery cycle, or, the compressor suction pressure P2
is greater than or equal to 10 psia, the controller 108 will
initiate the Cylinder Cool mode of operation.
In the Cylinder Cool mode, as indicated in FIG. 4, the solenoid
valves SVI and SV2 are energized and thereby in the open condition.
Solenoid valves SV3 and SV4 are closed, and, the compressor motor
and condenser fan motor continue to be energized. The Cylinder Cool
mode of operation essentially converts the system to a closed cycle
refrigeration system wherein the refrigerant storage cylinder 86
functions as a flooded evaporator. By closing solenoid valve SV3
the refrigerant recovery and purification system 10 is isolated
from the refrigeration system 12 being serviced The opening of
solenoid valve SVI establishes a fluid path between the vapor
outlet 88 of the storage cylinder 86 and the conduit 28 which is in
communication with the low pressure side of the compressor 44. The
closing of solenoid valve SV4 routes the refrigerant passing from
the condenser 60 through the refrigerant expansion device 74.
With the control solenoids set as described above, in the Cylinder
Cooling mode of operation the compressor 44 compresses low pressure
gaseous refrigerant entering the compressor and delivers a high
pressure gaseous refrigerant via conduit 50 to the oil separator
52. From the oil separator 52 the high pressure gaseous refrigerant
passes via conduit 56 to the condenser coil 60 where the hot
compressed gas condenses to a liquid. Liquified refrigerant leaves
the condensing coil 60 via conduit 66 and passes through the
T-connection 68 through the strainer 76 and, via conduit 72, to the
refrigerant expansion device 74. The thus condensed refrigerant, at
a high pressure, flows through the expansion device 74 where the
refrigerant undergoes a pressure drop, and is at least partially,
flashed to a vapor. The liquid-vapor mixture then flows via
conduits 78 and 82 to the refrigerant storage cylinder 86 where it
evaporates and absorbs heat from the refrigerant within the
cylinder 86 thereby cooling the refrigerant.
Low pressure refrigerant vapor then passes from the storage
cylinder 86, via vapor outlet port 88, through conduit 94 and
solenoid valve SVl to the T connection 96. From there it passes
through the check valve 98, solenoid valve SV2, oil separator/
accumulator 32, filter dryer 38 and conduit 40 to return to the
compressor 44, to complete the circuit.
As the Cylinder Cool mode of operation continues, the cylinder
temperature, as measured by the temperature transducer Tstor,
continues to drop as the refrigerant is continuously circulated
through the closed refrigeration circuit. Also during this time the
refrigerant is passed through the refrigeration purifying
components, i.e. the oil separator 32 and the filter dryer 38, a
plurality of times to thereby further purify the refrigerant.
Referring again to FIG. 2, the Cylinder Cool mode of operation will
terminate when any one of three conditions occur; 1) the cylinder
temperature, as measured by Tstor falls to a level 70.degree. F.
below ambient temperature (Tamb), or, 2) when the Cylinder Cooling
mode of operation has gone on for a duration of 15 minutes, or, 3)
when the cylinder temperature Tstor falls to 0.degree. F.
Regardless of which of the three conditions has triggered the
termination of the Cylinder Cool mode the result is substantially
the same, i.e., the temperature (Tstor) of the refrigerant stored
in the cylinder 86 is now well below ambient temperature. As a
result, the pressure within the cylinder, corresponding to the
lowered temperature is substantially lower than any other point in
the system.
When any one of the Cylinder Cool mode termination events occur,
the controller 108 will shift the system to a second Recover mode
of operation. In the second Recover mode the solenoid valves, and
compressor and condenser motors are energized as described above in
connection with the first Recover mode. Because of the low
temperature Tstor that has been created in the refrigerant storage
cylinder, however, the capability of the system to withdraw
refrigerant from the unit being serviced, without subjecting the
recovery compressor to high pressure differentials is dramatically
increased.
An understanding of this phenomenon will be appreciated with
reference to FIG. 1. It will be described by picking up a Recover
cycle at the point where refrigerant withdrawn from the system
being serviced is discharged from the compressor 44 and is passing,
via conduit 56, to the condenser 60. At this point the pressure
within the system, extending from the compressor discharge port 48
through to and including the storage cylinder 86, is dictated by
temperature and pressure conditions within the storage cylinder 86.
As a result the storage cylinder 86 now effectively serves as a
condenser with the recovered refrigerant passing as a super- heated
vapor through the condenser coil, through the solenoid valve SV4
and the conduits 80 and 82 to the storage cylinder 86 where it is
condensed to liquid form.
It is the dramatically lower compressor discharge pressure P3
experienced during a second or subsequent Recover mode (i.e. any
Recover mode following a Cylinder Cool mode) that allows the
recovery compressor 44 to draw the system being serviced 12 to a
pressure lower than heretofore obtainable while still maintaining a
permissible pressure ratio across the recovery compressor.
It will be appreciated that in a second Recover mode, the pressure
ratio P3/P2 could exceed the predetermined value (which in the
example given is 16) and, depending upon the other system
conditions, as outlined in the flow chart of FIG. 2, will result in
an additional Cylinder Cool mode of operation or termination.
With continued reference to FIG. 2, the system will then operate as
described until conditions exist which result in the controller 108
switching to the refrigerant contaminant test (Totaltest) mode of
operation. Prior to initiation of a Recover cycle an operator
should make sure that a sampling tube has been placed in the
sampling tube holder 104. Upon initiation of the TOTALTEST mode of
operation, solenoid valves SVl, SV2, SV4 and SV5/SV6 are all
energized to an open position The solenoid valve SV3 is not
energized and is therefore closed. With the flow control valves in
the condition described the flow of refrigerant through the
recovery system is similar to that described above in connection
with the Cylinder Cooling mode except that the solenoid valve SV4
is open and therefore the refrigerant does not pass through the
expansion device 74. With the refrigerant flowing through the
circuit in this manner, and with the solenoid valves SV5 and SV6
open, the pressure differential existing between the high and low
pressure side of the system induces a flow of refrigerant through
conduit 102 solenoid valve SV6, the sampling tube holder 104 (and
the tube contained therein), solenoid valve SV5 and conduit 106 to
thereby return the refrigerant being tested to the suction side of
the compressor 44.
A suitable orifice is provided in conduit 102, or in the sampling
tube holder 104, to provide the necessary pressure drop to assure
that the flow of refrigerant through the testing tube held in the
sampling tube holder 104 is at a rate that will assure that the
testing tube will receive the proper flow of refrigerant
therethrough during the TOTALTEST run time in order to assure a
reliable test of the quality of the refrigerant passing
therethrough With reference to FIG. 2 will be noted that the run
time of the refrigerant quality test is indicated as X minutes. The
normal run time for a commercially available TOTALTEST system is
about ten minutes and the controller may be programmed to run the
test for that length of time or different time for different
refrigerants. The quality test however may be terminated sooner if
the refrigerant being tested contains a large amount of acid and
the indicator in the test tube changes color in less than the
programmed run time. If this occurs, the refrigerant quality test
may be terminated, and, an additional refrigerant purification
cycle initiated.
The additional purification cycle is identified as the Recycle mode
and a flow chart showing the system operating logic is shown in
FIG. 3. With reference to FIG. 4 it will be noted that the
condition of the electrically actuable components is the same in
Recycle as it is for the Cylinder Cool mode except that the
solenoid valve SV4 is open so that the refrigerant does not flow
through the expansion device 74 but flows through the open solenoid
valve SV4. This increases the volume flow of refrigerant through
the system during the Recycle mode. The function of this mode is
strictly to further purify the refrigerant by multiple passes
through the oil trap 32 and the filter dryer 38.
With reference to FIG. 3 the length of time in which the system is
run in the Recycle mode is determined by the operator as a number
of minutes "X" which varies as a function of refrigerant type and
quality and ambient air temperature. The type of refrigerant is
known, the ambient temperature may be measured, and the quality is
determined by the operator upon the evaluation of the test tube
used in the refrigerant quality test cycle. With continued
referenced to FIG. 3, upon the end of the selected recycle time the
system, if so selected by the operator, will run another
refrigerant quality test, and, if the results of this test so
indicate another recycle period may initiated following the
procedure set forth above.
The object of the system and control scheme described above is to
remove as much refrigerant as possible from a system being
serviced, under any given ambient conditions, or system conditions,
while, at all times monitoring system control parameters which will
assure that the compressor of the Recovery system is not subjected
to adverse operating conditions. As described above, the system
control parameter is the pressure ratio P3/P2, across the recovery
compressor 44. In the example given above a value of P3/P2 of 16
was used as the pressure ratio above which the compressor could be
adversely affected. It should be appreciated that for different
compressors the value of this parameter could be different.
The ultimate goal in the control of this system is to limit
compressor operation to predetermined limits to assure long and
reliable compressor life. As pointed out above, in the Background
of the Invention, the internal compressor temperature is considered
by compressor experts to be the controlling factor in preventing
internal compressor damage during operation. In the presently
disclosed preferred embodiment the pressure ratio has been found to
be an extremely reliable effective control parameter which may be
related to the internal compressor temperature and has thus been
selected as the preferred control parameter in the above described
preferred embodiment. Pressure differential, (i.e. P.sub.3
-P.sub.2) could also be effectively used to control the system.
It should be appreciated however, that other system control
parameters such as the compressor discharge temperature as measured
by the temperature transducer 110 in the compressor discharge line
50, or the compressor suction pressure P2 could also be used to
control the operation of the system, to limit the system to
operation only at conditions at which the compressor is not
adversely effected.
With respect to temperature, it is generally agreed that an
internal compressor temperature at which the lubricating oil begins
to break down is about 325.degree. F. Above this temperature
adverse compressor operation and damage may be expected. In the
present system the controller 108 has been programmed such that,
should the compressor discharge temperature, monitored by the
temperature transducer 110 exceed a maximum of 225.degree. F.
regardless of pressure ratio conditions, the system will be shut
off.
It is further contemplated that, if the compressor discharge
temperature, as measured at the transducer 110 were used as the
primary system control parameter that a temperature in the
neighborhood of 200.degree. F. would be used to switch the recovery
system from a Recover mode to a Cylinder Cooling mode of operation
in order to assure that the compressor would not be adversely
affected during operation of the system.
According to another embodiment of the invention, as mentioned
above, the system control parameter being sensed for compressor
protection could be the compressor suction pressure P2. In this
case the microprocessor of the controller 108 would be programmed
with compressor suction pressures P2 which would be considered
indicative of adverse compressor operation, for a range of ambient
air temperatures and for the different refrigerants which may be
processed by the system. As an example, when processing refrigerant
R-22 at an ambient air temperature of 90.degree. F. a suction
pressure P2 in the range of 13 psia to 15 psia would be programmed
to change the system from a Recover mode cylinder Cooling mode of
operation.
The outstanding refrigerant recovery capability of a system
according to the present invention is reflected in the following
example. The recovery apparatus was connected to a refrigeration
system having a system charge of 4.5 pounds of refrigerant R-12 at
an ambient temperature of 70.degree. F. Such a system is typical of
an automobile air conditioning system.
Upon initiation of recovery the system performed a first Recover
cycle for 8.67 minutes before the system reached the limiting
pressure ratio P.sub.2 /P.sub.3 of 16. At that point 3.73 pounds
had been recovered from the system. This represents 82.9% of the
systems total charge. Typical prior art systems would stop at this
point, leaving 0.77 pounds, or more than 17% of the charge in the
system. This 0.77 pounds would eventually be released to the
atmosphere.
At this point, the system shifted to the Cylinder Cool mode of
operation. The Cylinder Cool cycle ran for 15 minutes, bringing the
cylinder temperature (Tstor) down to 10.degree. F. At this point a
second Recover cycle was initiated by the system controller. The
second Recover cycle ran for 3.8 minutes at which time Recover was
terminated when the suction pressure P2 fell to 4.0 psia.
At this point, the total system run time had been 27.5 minutes and
a total of 4.42 pounds of refrigerant had been recovered from the
system. This represents 98.2% of the total charge of 4.5 pounds,
leaving only 0.08 pounds in the system.
Following completion of recovery and purification, the storage
cylinder 86 contains clean refrigerant which may be returned to the
refrigeration system. With reference to FIG. 4, the Recharge mode,
when selected, results in simultaneous opening of valves SVI and
SV3 to establish a direct refrigerant path from the storage
cylinder 86 to the refrigeration system 12. All other valves and
the compressor and condenser are de-energized in this mode. The
amount of refrigerant to be delivered to the system is selected by
the operator, and, the controller 108, with input from the liquid
level sensor 92 will assure accurate recharge of the selected
quantity of refrigerant to the system.
This invention may be practiced or embodied in still other ways
without departing from the spirit or central character thereof. The
preferred embodiments described herein are therefore illustrative
and not restricted. The scope of the invention being indicated by
the appended claims and all variations which come within the
meaning of the claims are intended to be embraced therein.
* * * * *